CAIE A-Level Chemistry A2 24.1.1 The Identities of Substances Liberated During Questions

Practise predicting electrolysis products, writing balanced half-equations and explaining industrial diaphragm-cell operation.

Exam points

identify oxidation at the anode and reduction at the cathode, then write balanced half-equations with states and electrons
predict products for molten or aqueous electrolytes by comparing discharge of competing ions and the electrode conditions
explain industrial electrolysis observations, electrode materials and purification or diaphragm-cell arrangements

[Maximum number: 1]

Potassium iodide, KI, is used as a reagent in both inorganic and organic chemistry.

A student electrolyses a solution of KI(aq) for 8 minutes using a direct current. The half-equation for the reaction that occurs at the anode is given.

2 \mathrm{I}^{-}(\mathrm{aq}) \rightarrow \mathrm{I}_{2}(\mathrm{aq})+2 \mathrm{e}^{-}

Write a half-equation for the reaction that occurs at the cathode.

Include state symbols.

$2 \mathrm{H}^{+}(\mathrm{aq})+2 \mathrm{e}^{-} \rightarrow \mathrm{H}_{2}(\mathrm{~g})$ state symbols required

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CAIE A-Level Chemistry A2 24.1.1 The Identities of Substances Liberated During Questions question 1